Guys advice needed urgently.

The 2.5 Estate has started very suddenly using a lot of water,basicly on way to collect wife and babies and coolant low displayed on screen then temp gauge started to rapidly rise,checked expansion tank and it was empty so left it an hour or so and had breakdown people come out and check it over,no obvious signs of leaks (although there's a badly blistered pipe or far right of engine bay) and it took quite a few litres of water to get it back to normal level with car running.
Ive drove it too local garage and they have said its definitely head gasket (not too sure about them as they didn't want paying to test and that's before i took it in)...they say they did a water pressure test and chemical test and would like a £1000 to fix.

Car isn't blowing out white smoke at all and seems to run fine (with a close eye on water level) however there is a smell of what seems like exhaust gases in the car when blowers are on....could this be a genuine head gasket or possibly an oil cooler problem,seem to remember people mentioning misdiagnosed head gaskets before.
So basicly is there a definitive way of checking head gasket or oil cooler.

?
Finally if anyone local (ish) would like to earn some £££ then please feel free to pm me...have no faith in local garage and have to babies now stuck at home car less so need this fixing ASAP.
